This disclosure relates to forming protective coatings on articles, such as turbine engine components. Components that operate at high temperatures and under corrosive environments often include protective coatings. As an example, turbine engine components often include ceramic, aluminide, or other types of protective coatings. Chemical vapor deposition is one technique for forming the coating and involves pumping multiple reactive coating species into a chamber. The coating species react or decompose on the components in the chamber to produce the protective coating.